Large vehicles, such as trucks, are currently designed with a relatively large road clearance. One major reason for this is the need for using the vehicle for driving over rough terrain. At the front of the vehicle, the road clearance is normally on the order of 40-50 cm.
The fact that a truck normally has a relatively large road clearance constitutes a serious risk with respect to road traffic safety. The reason for this is that during a collision between such a truck and a passenger vehicle there is a risk that the passenger vehicle will penetrate in under (run under) the front or rear part of the truck and thus be jammed between the road surface and the underside of the frame or load carrier of the vehicle. The result may be that the rear part of the truck will enter the passenger compartment of the vehicle with great force, which in turn may cause serious injuries to the passengers of the vehicle. One purpose of an underrun protection device of this type is to prevent a vehicle from coming into contact with the frame during a collision event.
A further purpose is that the underrun protection device allows the normal zones of deformation of the colliding vehicle to be utilized.
Different solutions have been developed to solve the above problem. It is on one hand possible to design the truck with a lowered front or rear section, for instance, a rear section with a road clearance that is so low that there is no room for a passenger vehicle to penetrate in under the truck and be jammed between the truck and the road surface. Such a solution is, however, contrary to the above-mentioned desire for a large road clearance to facilitate driving over rough terrain. Hence, lowering the road clearance is therefore ruled out for many types of trucks.
A further solution to the problem in question is to provide the truck with a particular underrun protection device in the form of a reinforced structure, for instance in the shape of a horizontally arranged beam element at the rear section of the truck. By means of such an element it is possible to prevent a passenger vehicle from penetrating in under a front or rear section of a truck.
Such a reinforced structure may in addition be arranged to be energy absorbing so that the structure absorbs energy under load. This will further reduce the risk of serious injuries in a possible collision.
A known underrun protection device for trucks is disclosed in the German patent document DE4103782 C2. This underrun protection device includes a shock-absorbing element arranged under the front bumper of the truck. The shock-absorbing element can be set at a predetermined angle relative to the road surface. In the event of a collision with a passenger vehicle, the bumper will be acted on by a predetermined force which will cause a linkage to pivot the shock-absorbing element into a position preventing the passenger vehicle from penetrating under the truck.
Although this known design in principle gives a good protection against underrun for the passenger vehicle, it does have a disadvantage in that it requires a large number of moving parts, making it unnecessarily complicated and creating a risk of loss of function. Also, this solution gives little possibility for controlling the energy absorption in a controlled manner during a collision.
A further known underrun protection device for vehicles is known from the patent document DD 259 822. This system discloses two substantially S-shaped dampening elements, which are deformable and arranged between a spring attachment point on the vehicle and an underrun protection device. The dampening elements will deform under load in order to absorb force.
A further known underrun protection device for a vehicle is shown in the patent document EP 0 917 933. This document discloses a rear underrun protection device having a pair of load carrying elements with a fold-away section. This solution allows a deformation element to be partially folded away.
All the above documents show solutions in which a deformation element can be partially folded away. The problem with these types of underrun protection devices, however, is that they may obstruct a hook when connecting a trailer, or they may catch during a reversing operation towards an edge or a loading bay.
Hence, there is a need for an arrangement for providing underrun protection that when the need arises for increased road clearance, or connecting of trailers or similar components, the arrangement may be folded completely away, or at least almost completely away, while at the same time providing full protection against run-under by other vehicles during a collision.